Polyphosphonic acids have numerous applications in industry. For example, polyphosphonic acids can be used as corrosion inhibition agents in cooling water and boiler water systems (U.S. Pat. Nos. 4,446,046 and 4,201,669) and inhibitors of fouling deposit formation on jet engine components during the combustion of finished turbine combustion fuel oils (U.S. Pat. No. 5,596,130). One approach to the synthesis of polyphosphonic acids involves the radical polymerization of unsaturated phosphonic acid monomers (U.S. Pat. Nos. 4,201,669, 4,446,046 and 5,519,102).
An unsaturated phosphonic acid monomer that has received considerable attention is isopropenylphosphonic acid, which has the formula H2C═C(CH3)(PO3H2), which is referred to herein as “IPPA.” IPPA is currently prepared by reacting PCl3 with acetic acid and acetone (U.S. Pat. No. 4,446,046). This process, however, possesses numerous disadvantages. First, PCl3 is an extremely corrosive, hazardous, and toxic chemical. It requires special handling starting from transportation to storage to delivery to reactors. Any release of PCl3 would require immediate evacuation. Second, the process produces HCl and acetyl chloride, which are also very hazardous and volatile by-products. The process is further complicated since these by-products come out as a mixture and have to be scrubbed by water. This dilution magnifies the quantity of these by-products and leaves a mixture of HCl and acetyl chloride in water. Finally, PCl3 and the reaction by-products are very corrosive and require special equipment such as glass-lined reactors, condensers, scrubbers, collection tanks, etc. The use of PCl3 requires the use of equipment that is non-reactive with chlorides. Thus, equipment composed of other materials such as stainless steel cannot be used in the production of IPPA, which reduces large-scale commercial production capabilities.
Thus, it is desirable to have a process that produces phosphonic compounds that are precursors to polyphosphonic compounds on large scale that do not require the use of PCl3 and/or specialized equipment such as glass-lined reactors and accessories, etc. It would also be advantageous not to produce toxic, corrosive, and hazardous by-products during the synthesis of the phosphonic compound. Finally, it would be desirable to produce phosphonic compounds on commercial scale without special equipment such as glass-lined reactors. The methods described herein accomplish these goals.